INFLUENCE OF HIGH VOLUME FLY ASH AND NANOSILICA ON PARTICLE PACKING OF CONCRETE

摘要

The presence of high workability, durability and strength, are what qualifies concrete to be termed as high performance concrete. The rising need for high performance concrete in the construction industry, globally, has necessitated the exploration of different means to enhance concrete to this level of optimum performance. Durability can be improved through the use of supplementary cementitious materials. High volume fly ash (HVFA) is known to improve the durability of high strength concrete and Nanosilica (NS) efficiently improves the strength. This paper studies the efficiency of HVFA and NS in reducing the voids in concrete and this is ascertained through the means of a wet packing density test. The two part test involved determining the optimum packing density (PD) of concrete containing cement content from 13% to 21% at 2% intervals along with varying w/c ratios, in the first part. The second part involved replacing the cement content for a particular w/c ratio which produced maximum reduction in void ratio with 50% fly ash by weight. The HVFA concrete was also introduced with NS in varying percentages from 1% to 4% at an interval of 1% by weight of cementitious material. The test indicates a positive outcome in terms of reduction in voids by high volume fly ash and NS to a large extent.